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  • Per Enflo (b. 1944) is a Swedish mathematician working primarily in functional analysis, a field in which he solved several fundamental problems. Three of these problems had been open for more than forty years: The Basis Problem, The Approximation Problem and The Invariant Subspace Problem for Banach Spaces.
  • In solving these problems, Enflo developed new concepts and techniques, which were then used by other researchers in several mathematical fields, in algebra, number theory, classical and functional analysis, operator theory and in computer science, especially computer algebra and approximation algorithms. (see Wikipedia)


  • Per Enflo is also a renowned concert pianist, who has been concertizing for almost 70 years on five continents. Numerous recent recordings as soloist, soloist with orchestras, chamber musician and accompanist may be mentioned as well as a critic-acclaimed duo recital in Carnegie Hall, NY, with violinist Hristo Popov.


  • Enflo worked at Kent State University [1989-2012] where he held the title of University Professor. Enflo held earlier positions at the Miller Institute for Basic Research in Science at the University of California, Berkeley, Stanford University, Ecole Polytechnique, (Paris) and The Royal Institute of Technology, Stockholm.

Calendar 2025


Concerts in Bulgaria and Romania in October 2025

Robert Schumann Piano Concerto in a minor, Op. 54 and Mozart Piano Concerto No.14, KV 449



The 47th Summer Symposium in Real Analysis

June 16-20 2025, Complutense University of Madrid >>

  • The Real Analysis Exchange Website >>
  • The "Andy" 2025 >>


Årsmöte Svenska Matematikersamfundet

Annual meeting May 5 2025 Stockholm >>

  • Distinguished Lecture: Construction of Invariant Subpaces for Operators on Hilbert Space



Calendar 2024


Nordic Mini-Conference in Algebra, Analysis, and Geometry >>

November 6–8, 2024, MDU (Mälardalen University , Sweden)



Virginia Operator Theory and Complex Analysis Meeting on October 26, 2024  >>

  • Lectures in UVa, Charlottesville, VOTCAM 2024, Richmond, and Piano Recital October 25th 8 PM, Perkinson Recital Hall, University of Richmond



Visiting Speaker to the UK - June 3 to June 14 2024 >>

  • Wednesday, June 5 at 3:00 PM: Seminar at UCL (University College London)
  • Thursday, June 6 at 4:30 PM: Seminar at Oxford 
  • Tuesday, June 11 at 4:00 PM: Piano recital at Reading 
  • Wednesday, June 12 at 12 PM: Seminar at Reading



Copenhagen, Department of Mathematical Sciences, University of Copenhagen 2024

  • Special Analysis Lecture Wednesday, April17 >>   
  • Piano Recital, Thursday, April 18 >>



Proceedings of Symposia in Pure Mathematics, A Few Lines on Per Enflo’s Works >>

This book is dedicated to Professor Per. H. Enflo, who made significant contributions to functional analysis and operator theory



ON THE INVARIANT SUBSPACE PROBLEM IN HILBERT SPACES, PER H. ENFLO

Online: click here >> arXiv:2305.15442 [pdf,ps,other]

[Submitted on 24 May 2023 (v1), last revised 6 Apr 2024 (this version, v2)]



Calendar 2023


Craiova, Romania, the 20th October 2023, Ludwig van Beethoven, Piano Concert Concert no. 1 in C major for piano and orchestra, op. 15 with Filarmonica ”Oltenia” Craiova, director Svilen Simeonov

"Invited to participate as a soloist in the Concert no. 1 in C major for piano and orchestra, op. 15 of Ludwig van Beethoven was Per Enflo. A Swede settled in the United States, this respectable gentleman is not only a pianist so good that he has touched all the meridians of the world with his art, but also a renowned mathematician. Yes, mathematician. Two fields that seem so far apart, but which, at the highest level, approach asymptotically. Let us think only of Pythagoras and the sacred importance he attached to music. Per Enflo has not only a remarkable destiny, but also a long-lasting one, which I wish twice as long.

At 80, he still has the energy to let himself be swept up in the gaiety of Beethoven's composition with the enthusiasm of a toddler (until his piece began, he seemed to be struggling to resist the temptation to touch the keyboard). What is the secret of such a zest for life at such an advanced age? But perhaps that is not the question, but the answer. With his lordship's permission, I will also draw a parallel between the way he crossed his hands on the piano keys and the way of multiplying the means and extremes of a proportion.

Photos by my friend Daniel Botea, who, although he is incredibly old, enjoyed the same as me, like a child that is, all the wonders that the concert offered.

Autor: Iris Gottlieb



Valencia, Departamento de Análisis Matemático, Universidad de Valencia

  • WORKSHOP ON FUNCTIONAL ANALYSIS, November 16th 2023 >>
  • YouTube >>


Colloquium Centre for Mathematical Sciences, Lund University  September 13th 2023 >>


Helsinki, IWOTA 2023, University of Helsinki >>

July 31 - August 4, 34th International Workshop on Operator Theory and its Applications,

  • Semi-plenary session Tuesday August 1st
  • Concert August 3rd Conference Dinner 

Calendar 2022


A history of solving some famous problems in mathematical analysis

  • P H ENFLO
    Department of Mathematical Sciences, Kent State University, Kent, OH, USA and
    Instituto de Matemática Interdisciplinar, Facultad de Ciencias Matemáticas, Universidad Complutense de Madrid, Spain
  • M S MOSLEHIAN
    Department of Pure Mathematics, Center of Excellence in Analysis on Algebraic Structures (CEAAS), Ferdowsi University of Mashhad, Mashhad, Iran
    J B SEOANE-SEPÚLVEDA
    Instituto de Matemática Interdisciplinar (IMI), Facultad de Ciencias Matemáticas, Departamento de Análisis Matemático y Matemática Aplicada, Universidad Complutense de Madrid, Madrid, Spain
  • This paper provides a historical view of what functional analysis is, a biography of Per H. Enflo and a short view of four fundamental problems in the geometry of Banach spaces.


It gives the story of how Enflo, after several years of work, managed to solve three of these problems. It is a story of trying many ideas, testing them on simpler problems, trying to combine different techniques for handling different aspects of the problems, making many failed attempts and finally succeeding.


In 1966 Enflo found a general strategy for solving many problems in infinite dimensions, by combining appropriate finite-dimensional techniques with induction procedures. When applied to the old, fundamental problems in functional analysis, this has led to new concepts, problems, techniques and results in analysis. These developments have been applied also in several other areas of mathematics and computer science.

Mathematics >>         Music >>        Interviews & Reviews >>

Per Enflo - mathematician and concert pianist -

was the last laureate of a prize for solving scientific problem from the Scottish Book.


Invariant Subspace Problem in Hilbert Spaces:

Exploring Applications in Quantum Mechanics, Control Theory, Operator Algebras, Functional Analysis and Accelerator Physics - Mostafa Behtouei arXiv:2306.17023

"Per H. Enflo’s recent claim of solving the invariant subspace problem in his recent publication titled ”On the invariant subspace problem in Hilbert spaces.” [4] has generated excitement and anticipation in the mathematical community, as his work could represent a major breakthrough in the field. Enflo’s solution, if validated,would be a groundbreaking achievement in mathematics, resolving a longstanding problem and advancing our understanding of bounded linear operators on Hilbert spaces. Its impact would be significant and far-reaching." From: Mostafa Behtouei, 29 Jun 2023


When did you make the decision to go into math instead of music?

I have never made, and will never make, any such decision


  • "Mathematics and Music - What is the connection?"
    Lecture >> 31 August 2021, Science Festival Strömstad Academy Slides >
  • Beethoven last piano sonata Concert >> Strömstad Academy's Scientific Festival 2021


  • Mozart - Beethoven - Chopin Concert >>  Jubilee Congress of Polish Mathematicians on the 100th Anniversary of Polish Mathematical Society (2019, Krakow)


  • "An infinite-dimensional version of Hilbert's fifth problem with connections to non-linear geometry of Banach spaces"

    Lecture December 2021  Slides >> to Holiday Lecture by Per Enflo  via Zoom - Jani Virtanen (Reading and Helsinki) & Håkan Hedenmalm (KTH and Reading) 


Updated June23 2025 www.perenflo.com © 2011